Actually, you may be better off driving up the coast side of 101 - I live in Elma and it's a half-hour quicker for me to go through Aberdeen and Forks than it is through PA, because the roads are straighter and the traffic is lighter. Basically from I-5 take the Rochester exit (88) to highway 12, follow that to Elma and then to Aberdeen and head north on 101. Early morning and no traffic you can make the trip from Portland in less than 6 hours.